Hydrocarbon chlorides (such as methylene chloride, 1,1,1-trichloroethane, trichloroethylene, tetrachloroethylene and carbon tetrachloride) have been widely used as a dissolving agent of rubber and fatty acid or a cleaning agent for dry cleaning and precision machines and elements. The hydrocarbon chlorides have many advantages in low melting point, high solubility or detergency, non-combustibility and so on, but have some disadvantages in toxicity and carcinogenicity. They are therefore used under very limited conditions, e.g. limited concentration in drainage. Air pollution based on the hydrocarbon chlorides is also a big problem and very strict regulations have been applied since April in 1989 in Japan.
The hydrocarbon chlorides are recovered or removed by an active carbon adsorption method which, however, is insufficient because the adsorbing rate is poor and the recovering process is complicated.
Hydrocarbon fluorides or Freons (such as trichlorofluoromethane (Freon 11), trichlorotrifluoroethane (Freon 113) and dichlorodifluoromethane (Freon 12)) have also been widely used for spraying, refrigerant, a foaming agent, a solvent and a cleaning agent for IC or precision machine and elements. The hydrocarbon fluorides have a wide boiling point range within -40.degree. to 50.degree. C. and very low toxicity. They also have high solubility with oil and organic material and therefore exhibit very high detergency. Accordingly, the hydrocarbon fluorides are very important in recent industries.
However, in 1974, Professor Lorland of California University warned that Freon gas which was exhausted into air reached to the stratosphere without being decomposed in the troposphere and was decomposed a strong ultraviolet beam at the stratosphere, so as to cause the decomposition or destruction of the ozone layer. He added that the destruction of the ozone layer reduced the ultraviolet beam absorbing capacity of the ozone layer and adversely increased ultraviolet beam which reached to the earth's surface, so as to adversely affect the ecosystem. This means that, in respect to human beings, bad effects such as increase of skin cancer would be increased. He further warned that the destruction of the ozone layer is a public pollution on the whole earth. After that, many researches and studies have been conducted to find that ozone holes above the south pole and increase of skin cancer have been observed. AS the result, it is recognized that the phenomena are substantial and a serious threat to human beings, and have been considered as important problems in many international congresses, such as Montreal Protocol and Den Haag International Congress.
It is strongly desired to inhibit the use of some Freon and to develop Freon substitutes. It also has been intensely studied to recover Freon and not to exhaust it in the air.